The LSU AgCenter has received a U.S. Department of Agriculture grant to study weed management options in commercial sweet potato production.

The three-year grant for $67,000 came through the Louisiana Department of Agriculture and Forestry as part of a USDA program to support research in specialty crops, which include fruits, vegetables, nuts and nursery and horticultural crops.

The research will be conducted by LSU AgCenter weed scientist Donnie Miller and LSU AgCenter sweet potato specialist Tara Smith. The study will look at a comprehensive evaluation of herbicides labeled for use on sweet potatoes and the effects of spacing on weed management.

The project’s aim is to identify the best approach to manage problem weeds in sweet potatoes by combining current commercial herbicides with production practices, the researchers said.

Sweet potatoes are limited in the chemicals available to control weeds, Miller said.

“The amount of acres planted in sweet potatoes and the cost of getting label approval limit the efforts chemical companies take to get a product approved,” Miller said. “And sweet potatoes are in the same family as morning glory, so any chemical that kills that weed also would affect sweet potatoes.”

Along with evaluating different herbicides, the researchers also will be looking at timing of herbicide applications, spacing between plants and between rows, plant vine cover and individual varieties perform.

“Preferred size of the roots may dictate management strategies,” Smith said.

Plants that are planted closer together may produce smaller roots. At the same time, however, plants that are close together can create more shade between them earlier in the growing season and stifle weed growth.

ConAgra Foods Lamb Weston opened a state-of-the-art facility in Delhi, La., in August 2010 to process high-quality sweet potatoes in the heart of the Louisiana sweet potato-growing region to supply sweet potato products to food-service operators and retailers.

Market destination is more likely to dictate root size, Smith said. If producers grow sweet potatoes under contract, processors are going to want size uniformity and certain specifications that may differ from what the fresh market demands.

“We’re looking at production practices for weed management and applying the results to the processing sector,” Smith said. The results of the LSU AgCenter study will provide producers with the information they need to grow sweet potatoes that appeal to sweet potato processors.

The shift from what was almost exclusively a fresh-produce market to a processing market is changing the approach to sweet potato production, Miller said. “Potatoes for processing don’t have to have the same cosmetic appeal as fresh roots. They can have surface blemishes.”

The bottom line is producers will have to decide how much cosmetic appearance they’ll sacrifice for increased yield for the processing markets, Miller said. The research will look at “how much we can tweak or reduce herbicide use to meet the demands of the new processing system. Our results may change how growers approach growing sweet potatoes.”